Sled-agent: detect switch backend (tofino, softnpu, et al) at runtime - #11237

control: job assigned to worker 01M1QHHJ18887GVJ30CCVFF39R [factory aws, i-0dc624886e648c987] (queued for 46 s)
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task: starting task 0: "setup"
task: process exited: duration 4206 ms, exit code 0
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task: starting task 1: "rust-toolchain"
task: process exited: duration 15412 ms, exit code 0
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task: starting task 2: "authentication"
task: process exited: duration 22 ms, exit code 0
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task: starting task 3: "clone repository"
task: process exited: duration 14766 ms, exit code 0
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task: starting task 4: "build"
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| + unset TMPDIR
| + echo 'files in /var/tmp/omicron_tmp (none expected on success):'
| files in /var/tmp/omicron_tmp (none expected on success):
| + find /var/tmp/omicron_tmp -ls
| 136619   32 drwxr-xr-x   2 build    build           2 Sep  5 01:39 /var/tmp/omicron_tmp
| + rmdir /var/tmp/omicron_tmp
task: process exited: duration 1991388 ms, exit code 0
|W| found 6 output files
|W| uploading: /work/cargo-build-analysis.jsonl (1818646 bytes)
|W| uploaded: /work/cargo-build-analysis.jsonl
|W| uploading: /work/environment.json (108 bytes)
|W| uploaded: /work/environment.json
|W| uploading: /work/oxidecomputer/omicron/target/nextest/ci/junit.xml (674189 bytes)
|W| uploaded: /work/oxidecomputer/omicron/target/nextest/ci/junit.xml
|W| uploading: /work/oxidecomputer/omicron/target/live-tests-archive.tgz (284238336 bytes)
|W| uploaded: /work/oxidecomputer/omicron/target/live-tests-archive.tgz
|W| uploading: /tmp/nextest-run-archive.zip (3218759 bytes)
|W| uploaded: /tmp/nextest-run-archive.zip
|W| uploading: /tmp/nextest-chrome-trace.json (4292160 bytes)
|W| uploaded: /tmp/nextest-chrome-trace.json